This invention relates generally to a laser control apparatus and more particularly to an apparatus used to stabilize and to switch a CO.sub.2 laser between a plurality of different R/P line pairs.
A use of a stabilization and switching circuit is mentioned briefly in an article by C. W. Gillard et al., Absolute Distance Interferometry, Optical Engineering, January/February 81, Vol. 20, No. 1, pages 129 to 134. The need for such a circuit was created because a two-color laser had to operate simultaneously on several R and P line wavelength sets. The absolute distance sensor mentioned in the above article using this type of circuit is composed of a CO.sub.2 laser, two frequency driven Bragg cells, a synthetic Michelson interferometer, and a pair of detectors that detect the R and P line beams. The two-color laser of the above sensor is capable of stabilizing and operating simultaneously on any of four sets of two-color pairs, and of switching through the various color pairs by means of a piezoelectric mirror drive and control subsystem.
The piezoelectric mirror drive causes the two-color laser to shift operating points. An R/P differential power detector receiving a portion of the two-color laser energy outputs a signal to control electronics that adjust the piezoelectric mirror drive according to stabilization and switching requirements.